THR premieres a scene from Sunday's episode, which features guest star Stephen Lang.

After discovering that the coven is conspiring behind her back, Mary (Janet Montgomery) -- in a scene from Sunday's episodeexclusive to The Hollywood Reporter -- takes matters into her own hands.

In a tense confrontation with Magistrate Hale (Xander Berkeley), Mary lays down the law. After all, it's her who got the witches on the path to achieving the Grand Rite, a point she has no problem making.

"Much worse for you, you underestimated me," Mary says.

"Do you have any idea what you've done?" Hale pleads.

"Question isn't whether I understand what I've done, but whether you understand what you must now do," Mary says in a final warning.